General theory of Relativity (GR) is a field theory, one of the first of its kind, that is classified under classical physics. The validity of the theory ranges from solar system length scales to cosmological length scales. It has passed most of its predictions with flying colors, starting from the extra perihelion precession of Mercury in the inner solar system [1]}, to gravitational lensing [2]}, to the generation of gravitational waves (GW) [3]},[4]}, [5]}, [6]}, [7]}, [8]}, and finally to the existence of objects called black holes (BH) [9]}.
